FIG. 1 is a schematic view showing the structure of a wind turbine generator system in the conventional technology. As shown in FIG. 1, the wind turbine generator system includes a nacelle 11, a generator 12, a cooling device 13, an air extraction pipe 14, a base 15, a tower 16, a hub 17 and a blade 18. The cooling device 13, the air extraction pipe 14 and the base 15 are arranged in the nacelle 11. The nacelle 11 is arranged on the tower 16 via the base 15, and the tower 16 is used to support the nacelle 11. The blade 18 is connected to the generator 12 via the hub 17, and the blade 18 rotates to drive a rotor shaft of the generator 12 to rotate to produce electricity. The generator 12 is a major energy conversion component of the wind turbine generator system, but also a major heat generating component, that is, the generator 12 generates heat during operation. To ensure the normal operation of the generator 12, a cooling system is required to cool the generator 12. As shown in FIG. 1, the cooling device 13 and the air extraction pipe 14 are used to cool the generator 12. The air extraction pipe 14 has one end connected to the generator 12 and another end connected to the cooling device 13, and the air extraction pipe 14 is used to extract hot air generated by the generator 12 during operation and convey the hot air into the cooling device 13. The hot air is cooled by external air flow flowing in a cooling air flow passage 19 arranged in the cooling device 13, and the cooling device 13 conveys the obtained cold air back to the generator 12 to cool the generator 12. The conventional cooling system for a wind turbine generator system is an air-air heat exchange system.
When the wind turbine generator system is in a high-temperature environment, a temperature difference between the ambient temperature and the generator temperature is small, which leads to a poor cooling effect of the external air flow in the cooling air flow passage on the hot air generated by the generator, thereby reducing the cooling efficiency of the generator.
When the wind turbine generator system is in a low-temperature environment, the temperature difference between the ambient temperature and the generator temperature is large, thus the system for cooling the wind turbine generator system may stop, and the hot air generated by the generator may dissipate into the environment due to the large temperature difference, thereby cooling the generator. In this case, if the wind turbine generator system stops, the temperature in the nacelle will be close to the ambient temperature, and before restarting the wind turbine generator system, the temperature in the nacelle needs to be raised to the normal operating temperature for various parts and components and electrical elements. Generally, to make the temperature in the nacelle reach the operating temperature for various components, multiple independent heating devices need to be provided for parts and components of the wind turbine generator system, which will increase the cost and energy consumption.